MAC Curves for different technologies and sectors

[fkanyako]

Hi,
Is it possible to generate CO2 MAC Curves for different GCAM sectors and the technologies contributing to that Curve for each sector? How do I set this up in GCAM?

Thank you.

[pkyle]

A marginal abatement curve with 5 points can be constructed for a scenario with a known set of carbon prices by re-running the model at 0%, 25%, 50%, and 75% of the carbon prices observed or assigned in each time period. The curve is constructed in any time period using the CO2 prices ($/t) on the y-axis, and the abatement observed in the given sector on the x-axis, where the abatement is equal to emissions with zero carbon price minus the emissions observed in the given scenario. So it's pretty simple, albeit time-consuming, and with several pitfalls.

1. When you query CO2 emissions by sector, CO2 emissions from biomass-derived carbon are reported as CO2 emissions, so you'll want to devise some method of deducting these emissions which are relevant for any sectors/technologies consuming biomass and/or liquid fuels.
2. A lot of the abatement in a scenario happens upstream of end-use sectors, and you might want to include this in your sectoral abatement curves. For example, the buildings sector consumes a lot of electricity, whose average carbon intensity will drop as the CO2 prices go from 0% to 100% of the scenario level. However in a query of CO2 emissions by sector, the technologies that consume electricity will be assigned zero emissions, even in the baseline, because upstream emissions are not assigned to the end-use sectors. So, a MAC curve constructed from the "direct" emissions from buildings, as reported by the model query, will have a lot less abatement taking place than one that also includes the "indirect" emissions from producing electricity.
   The methods of performing such an analysis will determine the conclusions that can and should be drawn from it. In scenarios with economy-wide CO2 prices, abatement doesn't happen on a sector-specific basis, and while the model does report emissions that could be used to sketch out a marginal CO2 abatement cost curve, it is worth considering whether and how to incorporate some of the relevant upstream changes into the estimated sector-specific abatement response.